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Subject: Re: New mode DM-Verity error handling
To:     Milan Broz <gmazyland@gmail.com>,
        Mike Snitzer <snitzer@redhat.com>,
        Sami Tolvanen <samitolvanen@google.com>
Cc:     dm-devel@redhat.com, linux-doc@vger.kernel.org,
        linux-kernel@vger.kernel.org, agk@redhat.com, corbet@lwn.net
From:   JeongHyeon Lee <jhs2.lee@samsung.com>
Message-ID: <250156a6-a2d6-dbfd-daa3-be9c36f0cf36@samsung.com>
Date:   Tue, 23 Jun 2020 08:53:32 +0900
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Dear Milan Broz.

Thank for your reply.


I didn't understand well, could you explain it in more detail?

For what reason isn't panic better?

Is it because there is a place to use other device-mapper?

Or other things? I just wonder. I would like to hear various 
explanations and information.


I just wanted user to use what they wanted through the options(flags).

Yes, If adding a new feature, modify user-space to support.


Oh, I'm sorry :(

If when i suggested new patch, i will send you a patch that increased 
minor version.

Thank you for all your detailed information.


Thanks.

JeongHyeon Lee


On 22/06/2020 16:58, Milan Broz wrote:
> On 18/06/2020 19:09, Mike Snitzer wrote:
>> On Thu, Jun 18 2020 at 12:50pm -0400,
>> Sami Tolvanen <samitolvanen@google.com> wrote:
>>
>>> On Thu, Jun 18, 2020 at 11:44:45AM -0400, Mike Snitzer wrote:
>>>> I do not accept that panicing the system because of verity failure is
>>>> reasonable.
>>>>
>>>> In fact, even rebooting (via DM_VERITY_MODE_RESTART) looks very wrong.
>>>>
>>>> The device should be put in a failed state and left for admin recovery.
>>> That's exactly how the restart mode works on some Android devices. The
>>> bootloader sees the verification error and puts the device in recovery
>>> mode. Using the restart mode on systems without firmware support won't
>>> make sense, obviously.
>> OK, so I need further justification from Samsung why they are asking for
>> this panic mode.
> I think when we have reboot already, panic is not much better :-)
>
> Just please note that dm-verity is used not only in Android world (with own tooling)
> but in normal Linux distributions, and I need to modify userspace (veritysetup) to support
> and recognize this flag.
>
> Please *always* increase minor dm-verity target version when adding a new feature
> - we can then provide some better hint if it is not supported.
>
> Thanks,
> Milan
>
>